Leukotrienes are inflammatory mediators, produced by inflammation, which in turn can induce inflammation. Scientists have found that leukotrienes play an important role in the development of asthma and allergic rhinitis. Therefore, they tried to use anti-leukotriene drugs (or leukotriene antagonists) to treat asthma and allergic rhinitis with good results (the current instructions of anti-leukotriene drugs basically say that they are used to treat asthma). In recent years, some scientists have found leukotriene receptors (molecular structures that bind easily to leukotrienes) on the surface of adenoids, so they wondered if adenoid hypertrophy was also related to leukotrienes. They stimulated the cells of the adenoids with leukotrienes and found that the T-lymphocytes inside the adenoids grew rapidly; if anti-leukotriene drugs were used, these lymphocytes decreased. Results from clinical trials have also shown that taking anti-leukotriene drugs can lead to significant improvement in symptoms of adenoid hypertrophy, especially in children with mild to moderate adenoid hypertrophy. We have been using anti-leukotriene medications for children with adenoid hypertrophy since 2012 and have received good results, with many children avoiding surgery as a result. The most commonly used anti-leukotriene medication is montelukast (Merck Sharp & Dohme, under the trade name of Sunnin), which comes in three sizes: 4mg (for ages 2-6 years), 5mg (for ages 6-14 years) and 10mg (for ages 14 years and older). Sometimes it can be used for more than 2 years if combined with allergic rhinitis or asthma. The most common side effects are euphoria and difficulty sleeping, and should be discontinued as soon as similar symptoms are noticed. The side effects will disappear within a few days after stopping the drug.